1. Field of the Invention
The present invention is directed to an industrial apparatus for preserving perishables, such as fresh squeezed citrus and non-citrus fruit juices, fruit juice blends, fruit pulp, dairy products, barley products, soups, and soft drinks. More particularly, the industrial apparatus enables a thermal preservation process for aseptically packaging perishables without adding preservatives.
The invention also encompasses an industrial apparatus for treating perishable products (including fruit juice, fruit juice blends, fruit pulp, wines, milk, chocolate milk, butter, yogurt, cultured milk products, beer, malt and oat beverages, soups, and soft drinks) in order to extend their shelf-life.
2. Description of the Prior Art
When fruits are harvested, microbiological and chemical changes occur which limit the time the fruit remains acceptable to the consumer and is safe for consumption. Since most of the post-harvest changes in food lead to spoilage, various methods of food preservation are used to prolong the length of time for which the foods retain their original quality and appeal.
In the days of simple farming communities, the population lived on locally grown fruits and vegetables. As a result, no highly organized methods of food preservation were necessary.
In the modern world however, centers of world population are in towns and cities, that are often many miles from the main areas of food production. To provide unspoiled food to these distant consumers, methods and chemicals were developed to preserve food. Unfortunately, long-term tests have shown how these same chemicals can harm the very people intended to be protected.
After harvesting, plant tissue is unable to prevent the attack of microorganisms such as bacteria, yeast, and molds, which break down the food structure and produce undesirable "off-flavors," discoloration, and odors. The number of organisms in an ounce of food can range from several hundred to twenty million or more and the organisms are capable of rapid multiplication, such that under certain conditions, their numbers can double every fifteen or twenty minutes.
Bacteria are minute microorganisms that are the most common cause of food spoilage. Bacteria also can render the food unpleasant to eat. And, in the case of pathogenic bacteria, such as Staphylococcus aureus or Clostridium botulinum, bacteria may cause far worse effects including food poisoning.
Food spoilage is also caused by chemical substances known as enzymes which are always present in minute quantities in living materials. Enzymes are proteins that catalyze biochemical reactions. Enzymes catalyze the chemical reactions that change the flavor and texture of fruits during ripening. Enzymes are also responsible for the deterioration of fruits after harvesting, such as the browning of the cut surface of apples and pears caused by the oxidation of phenols by the enzyme phenolase.
Because enzymes are proteins, enzymes are heat sensitive. Most proteins irreversibly denature when heated above normal biological temperatures. When proteins denature, they unravel and lose their three-dimensional shape. Because the ability to catalyze reactions depends on shape, once enzymes are heated, they usually lose their ability to catalyze reactions.
Thermal preservation techniques for rendering inactive bacteria and enzymes in fruit juices and citrus pulp typically rely on known, large-scale, pasteurization techniques. Pasteurization is a heat treatment process, wherein a supply of food product is heated in stainless steel containers at temperatures normally less than 212.degree. F. (100.degree. C.). Although common pasteurization techniques destroy pathogenic organisms, they do not provide indefinite protection against microbiological spoilage. Products that have been pasteurized need to be refrigerated immediately. Pasteurization extends shelf life to four to seven days in diary products and four to six weeks in fruit products.
Even an acidic product, such as fruit juice, requires protection from spoilage organisms such as acetobacter, whose growth can lead to cloudiness in the fruit juice product. Cloudiness in some citrus juice products is due to the presence of pectin, which occurs naturally in the fruit. If the natural pectolytic enzymes of the fruit are not destroyed, they degrade the pectin with the result that the juice becomes cloudy and often gels. Therefore, in order to destroy the pectolytic enzymes, most citrus juices are processed by flash pasteurizing in a plate heat exchanger at 203.degree. F. (95.degree. C.) for 30 seconds. However, while partially rendering enzymes organically inactive, this process degrades juice quality since the juice in contact with metallic heat exchanger elements reach temperatures above 100.degree. C. The product that directly contacts the heating surface may actually become cooked if exposed to heat for more than thirty seconds. Cooking causes irreversible changes in the taste, color, and odor of food. Furthermore, the prior art methods have been found unsatisfactory for rendering the enzymes present in citrus and non-citrus fruit juices organically inactive or destroying bacteria and other pathogenic and non-pathogenic organisms. The short shelf life of pasteurized products evinces the shortcomings of current methods.
Placing heating elements in direct contact with malt beverages also may alter the taste, color, and odor. When malt beverages such as beer are directly heated by heating elements that are above one-hundred-sixty-five degrees centigrade (165.degree. C.), the original taste becomes affected. To prevent overheating, malt beverages may not be fully pasteurized with the result that many harmful bacteria and enzymes remain. Fresh barley products have a similar shelf life to milk.
Pasteurization techniques do not render one-hundred percent of the enzymes in these products organically inactive. As a result, certain fruit juices have not been made readily available to the consuming public due to the limited success of the prior art methods. For example, juices such as watermelon juice, banana juice, grape juice, and pineapple juice are not found on store shelves packaged in a one hundred percent natural state. Oftentimes, the juice quality is compromised by the addition of various preservatives to maintain freshness and color.
Fresh dairy products may be more sensitive to enzymes than fruit products. Pasteurized milk only lasts four to seven days even when refrigerated.
Thus, a need still exists for an industrial apparatus for the thermal processing of fresh fruit products, fresh dairy products, and fresh barley products which will result in the aseptic packing of these products without the addition of preservatives to extend the shelf life of the products up to two to three years without refrigeration.